The present invention relates to a device in a quick coupling for detachably coupling a working implement to the operating arm of an excavating machine, said quick coupling comprising two parallel link arms supported by the operating arm, each link arm having an abutment portion with a support surface, and a locking means comprising a stationary wedge support attached to the working implement with an engagement surface facing the working implement and a movable tension pin displaceable by a power cylinder and having an engagement surface for wedging cooperation with the engagement surface of the wedge support, said locking means having support surfaces to cooperate by means of pressure with the support surfaces of the link arms.
A quick coupling of the type described above has proved advantageous in several respects and has enjoyed wide practical use. It has the following advantages, for instance It has extremely low weight (about 30 kgs for a machine up to 14 tons) and therefore saves material, as well as being light to use and assamble; the construction is simple, making it quick and easy to mount the bucket to the excavating machine; it has no intermediate elevational piece which would cause building height and increased weight; thanks to its low weight it does not necessitate altering the bucket volume; it enables the force-absorbing dome of the bucket to be retained, thanks to the link arm construction in that the link arms may have an arc-shape adapted to the dome; it entails improved, even optimum conditions for the force transmission between bucket and operating arm and the link arms are not affected to any noticeable extent since the forces are transmitted directly to the hooks from the stick and vice versa via the stick shaft and sleeve, if any, abutting the hooks; thanks to its design and to said improved force transmission, the stipulated geometry of the bucket can be retained; it withstands diagonal breaking movements of the bucket since the link arms make the coupling resilient, because of the fact that the link arms have no rigid, stiffening joint between them and they can therefore move freely up and down at their end portions at the four contact points with the bucket, independently and in relation to each other and will thus always follow the diagonal breaking movements of the bucket when this is temporarily deformed and becomes distorted by lateral point stresses during work; it maintains a play-free joint between implement and operating arm at the contact points between operating-arm attachment means and hooks, even when the link arms follow the diagonal breaking movements of the bucket; it is self-adjusting with respect to any slight wear which may occur at the contact surfaces, and a play-free joint is thus always guaranteed.
The quick coupling described above and known through patent specification EP 0 139 652 is designed for manual locking with the aid of a wedge-like tension pin which the operator forces into the desired locking position in the quick coupling with the aid of a suitable tool. Although the manual effort required is relatively little, there has been increased demand for the actual locking step with the tension pin to be carried out automatically from the driver's cab. The problem has been to achieve a hydraulically controlled locking device which is reliable to use, simple to manufacture and install, can be mounted without affecting the other features and functions of the quick coupling, does not increase the dimensions of the quick coupling, can be mounted in a protected place to avoid damage and dirt and which is relatively inexpensive to manufacture.
The object of the present invention is to provide a locking device for a quick coupling of hydraulic or pneumatic type which can be operated from the driver's cab, and which solves the problem mentioned above. An essential advantage of the locking device according to the invention is also that it can be manufactured as an ancillary unit for already existing quick couplings, thus converting them simply from manual to hydraulic or pneumatic insertion of the tension pin without any structural alterations having to be performed on the quick coupling.
This is obtained according to the present invention in that the locking means comprises a locking unit supported by the link arms, said locking unit having a rigid housing extending between the link arms, in which the tension pin is axially displaceable by the power cylinder between, in relation to the wedge support, an outer free position and an inner locking position, said housing having an opening located at a central portion thereof and disposed vertically in line with the wedge support of the working implement for friction-free receipt of the wedge support therein when the tension pin is in its free position, that the housing is provided with opposite supporting pins axially aligned to each other and arranged removably and with clearence freely to be received in opposite openings in the link arms, said supporting pins and openings being provided with said pressure-cooperating support surfaces, that the tension pin is of such sufficient length that its front end portion located at the engagement surface in locking position of the tension pin is positioned in a cavity of the housing and has a support surface for pressure-cooperation with a support surface in the cavity, and that one of the supporting pins is provided with a through-hole to receive a rear end portion of the tension pin in its locking position.